Influence of Vegetation Type and Park Age on Soil Dissolved Organic Matter Composition in Subtropical Urban Parks

ABSTRACT The chemical characteristics of dissolved organic matter (DOM) play a key role in soil nutrient cycling and carbon sequestration. However, the effects of different vegetation types and park ages on soil DOM in urban ecosystems remain poorly understood. This study assessed the influence of two vegetation types, lawn and integrated tree‐turf systems, on the chemical characteristics of soil DOM across three park age groups (young: 5–10 years, intermediate: 11–20 years, and old: > 21 years) in Ningbo city in eastern China. DOM chemical characteristics were analyzed using UV–visible absorption and fluorescence excitation emission matrix‐parallel factor analysis. Results showed that both vegetation type and park age significantly influenced the chemical properties of soil DOM. The highest soil dissolved organic carbon content (0.82 ± 0.15 g kg −1 ) was found in integrated tree‐turf systems in the oldest parks. Specific ultraviolet absorbance‐254 values < 3, humification index values < 1, and biological index values mostly < 1, alongside protein‐like (C2) substances comprising 38%–51%, indicated low humification, weak aromaticity, and pronounced autochthonous characteristics. As park age increased, more humic‐like DOM (C1) content was found in integrated tree‐turf system soils, while protein‐like substances decreased. In contrast, protein‐like substances dominated DOM in lawn soils. pH and soil moisture significantly affected DOM chemical characteristics. These findings enhance our understanding of the factors shaping DOM in urban green space soils.